"Bob Adkins" wrote in message
...
On Sun, 16 Jul 2006 12:02:02 -0400, Neon John wrote:


When I can buy a pack of 5 from Sam's for $9, only a bit more than an
equivalent incandescent, the enconomics become a no-brainer.

I use Sylvania and GE, and sometimes they go out within a month. I do have
1
good CF that must be 7-8 years old, but most don't last a year.

What brands could you recommend that last longer than Sylvania and GE?

Sorry to hear yours don't work out so well.

I buy the 'whatever' brand at Wal---- and they last several years for me.
The ones in the kitchen are the shortest lived because the fixture has an
enclosed 'globe' that seems to hold the heat in and shorten their life. But
even at that I get 18 months to 2 years from them.

daestrom

"Don Klipstein" wrote in message ...

I would like to add: Watch out for overheating CFs by putting them in
small enclosed fixtures and in downlights. Many CFs don't take this well,
and there is a general trend that this is worse with higher wattages.

Some actually rated to take the heat of recessed ceiling fixtures are
Philips SLS non-dimmables up to 23 watts.

I consider it notable that when I see recessed ceiling fixtures in
commercial buildings with CFs, the bulbs usually do not have built-in
ballasts and will not screw into "regular sockets". The ballast is
somewhere else in the fixture where it will not get as hot.


Why can't they use components that compensate for the heat?

Don

"Mary Fisher" wrote in message
t...

"Don K" wrote in message
. ..

The one in the hallway went out after about a year and a half to two
years. I don't know where my receipt is, so I guess I'm out a few bucks.

These CFL's sure are frugal. Just make sure you send in any rebates
and keep track of your receipts and the packing material for the
next 9 years.

We pencil the installed date and the supplier on the item itself. We've only twice had to return
them and they've been replaced with no receipt and no question.

Customer goodwill is important to stores. The items are cheap and it's recognised that some will
fail.

Mary

It's worth a try. I'll just take it back next trip to the 'depot.
Thanks

Don

Watch out for overheating CFs
by putting them in small enclosed fixtures and in downlights.
Don Klipstein

Why can't they use components that compensate for the heat?
Don K

Perhaps you mean *tolerate* the heat or *disipate* the heat.

The former could mean more exotic materials.
Silicon Carbide semiconductors are being developed
which operate over a wider temperature range.
They will, of course, be more expensive than old-school parts.

The latter requires more surface area
so that the heat will be more readily radiated to ambient.
This means that the volume of the product must increase
to accomodate a larger heatsink and/or venilation must be increased.

In a strongly competetive market,
these options don't look especially attractive to most manufacturers.
As the word spreads about the problems that these products have
and if a repository of comparative data is established,
perhaps things will change for the better.
I won't be holding my breath.

In article , Don K wrote:
"Don Klipstein" wrote in message
...

I would like to add: Watch out for overheating CFs by putting them in
small enclosed fixtures and in downlights. Many CFs don't take this well,
and there is a general trend that this is worse with higher wattages.

Some actually rated to take the heat of recessed ceiling fixtures are
Philips SLS non-dimmables up to 23 watts.

I consider it notable that when I see recessed ceiling fixtures in
commercial buildings with CFs, the bulbs usually do not have built-in
ballasts and will not screw into "regular sockets". The ballast is
somewhere else in the fixture where it will not get as hot.


Why can't they use components that compensate for the heat?

Don

I think that the problem is finding components that have low failure
rate after 6,000 or 10,000 hours of working at internal chip temperatures
roughly 150 degrees C or close to 300 degrees F.

The junctions within the semiconductor devices will be significantly
hotter than the surfaces or the leads of those.

The surfaces and leads of heat-producing transistors (or other
semiconductors) have to be hotter than the air inside the "base"/"ballast
housing" that houses those things.

The air inside the housing has to be hotter than the inside surface of
the housing.

The inside surface of the housing has to be hotter than the outside
surface of the housing. Looks like I gotta take my "Ray Tek" infrared
non-contact thermometer to see how hot that is when a CF is crewed into
a recessed ceiling fixture or a small enclosedfixture...

Meanwhile, that has to be hotter than the air around that, and it gets
awfuklly warm in the upper regions of recessed ceiling fixtures!

Heat has to "flow downhill" (from higher temp to lower temp).
Transistors and other semiconductors with silicon main chip material and
the usual epoxy molded surrounding body are usually rated to only 150
degrees C junction temperature. Some metal case ones are rated to 200 C
junction temperature, but often (maybe normally) with unimpressive life
expectancy figures when pushed that hot, as well as higher cost.

Silicon carbide semiconductors take much higher temperatures very well,
but so far "The Market" has decided that in most cases silicon carbide
power semiconductors (with cases and encapsulants that take such heat and
tolerate warping from big temperature changes occurring unevenly
throughout the semiconductor package) are too exotic and expensive in
comparison to making do with silicon and epoxy molded packages for them.

The alternative is "inductor"/"choke"/"reactor" ballast rather than
an electronic one, wound with "magnet wire" having insulation and having
any interlayer insulation and insulation between winding and core and the
winding bobbin rated for really high temperatures. Keep in mind that such
ballasts have lower efficiency than magnetic ballasts and they can vibrate
unless extra work is done to minimize that and a few people are bothered
by the AC flicker from fluorescent lamps with ballasts other than
electronic ones using high frequencies.

- Don Klipstein (not Don K) )

On 17 Jul 2006 16:01:23 -0700, "JeffM" wrote:

Watch out for overheating CFs
by putting them in small enclosed fixtures and in downlights.
Don Klipstein

Why can't they use components that compensate for the heat?
Don K

Perhaps you mean *tolerate* the heat or *disipate* the heat.

The former could mean more exotic materials.
Silicon Carbide semiconductors are being developed
which operate over a wider temperature range.
They will, of course, be more expensive than old-school parts.

It wouldn't matter how well the (CF) unit "dissipates" the heat
if it's in an enclosed fixture.
( you'd have to look into how well the fixture dissipates the heat )

On the bright side, lets say a fixture is rated for "60 watt max" bulb,
then a 60W CFL which only creates 18(?) watts of heat
should have a pretty comfortable factor. ????

As for hi-temp components....
most commercial grade electronic components
should be good up to "boiling" ( 212f )
except of capacitors.... ( I don't know about modern caps )


rj

In article ,
wrote:

On the bright side, lets say a fixture is rated for "60 watt max" bulb,
then a 60W CFL which only creates 18(?) watts of heat
should have a pretty comfortable factor. ????

Turns out, a 42 watt CFL heats a fixture about as much as, or even a bit
more than, a 60 watt incandescent. A CFL produces little infrared.

Of course, how much a lamp heats up the house is determined by wattage
alone.

A downlight fixture at its temperature limit will almost certainly bake
a CFL to death pretty quickly.

As for hi-temp components....
most commercial grade electronic components
should be good up to "boiling" ( 212f )
except of capacitors.... ( I don't know about modern caps )

Most semiconductors are rated good to a junction temperature of 150 C,
or 302 F. Oc course, the surface of the semiconductor has to be cooler
than that in order for heat to flow out. And the air around the
semiconductor has to be even cooler, the inside surface of the ballast
housing has to be even cooler, and the outside surface of the ballast
housing has to be cooler still.

Decent electrolytic capacitors are rated for 105 degrees C but usually
only a few thousand hours life expectancy at that temperature. CFL
manufacturers have put a lot of work into finding capacitors that hold up
well enough to not do too much damage to their reputations.

- Don Klipstein )